The present invention relates to hard disk drive pivoting head arm assemblies.
In a hard disk drive, one or more disks are mounted on a spindle for rotation. Heads for reading and writing data onto the disks are mounted on the end of a head arm which swings across the surface of the disk. In a typical arrangement, the head arm is mounted to rotate about a pivot axis so that the heads will swing across the surface of the disk in an arcuate path.
Such a pivot axis runs through the middle of a central shaft which is surrounded by a pair of ball bearing rings. A cylinder coupled to the head arm is mounted around the ball bearing rings for rotation. Also connected to the cylinder opposite the head arms is an actuator coil which passes between some permanent magnets. By applying the proper current to the coil, the magnetic fields generated by the coil and the permanent magnets interact, causing the head arm assembly to rotate.
Because the heads ride very close to the surface of the disks, it is important that the head arm assembly not vibrate or tilt and damage the disk. A tilt would also cause mistranslation between the position sensing servo head and the data heads which are referenced to the servo heads for position. A vertical biasing spring is typically inserted between the two ball bearings to exert a vertical loading force on the ball bearings, thus preventing up and down movement or vibration which could damage the disks or impair the effectiveness of the heads.